U.S. patent number 4,065,824 [Application Number 05/711,477] was granted by the patent office on 1978-01-03 for lip extender for loading dock levelers.
This patent grant is currently assigned to Ellis Industries, Inc.. Invention is credited to Lawrence D. Ellis, Robert E. Evans.
United States Patent |
4,065,824 |
Ellis , et al. |
January 3, 1978 |
Lip extender for loading dock levelers
Abstract
A lip extender for use with a loading dock leveler. The lip
extender includes a lower link connected at its lower end to the
base plate of the leveler and a toggle arm connected at its upper
end beneath the lip. The opposite ends of the toggle arm and lower
link are pivotally connected together. Upward movement of the hinge
connection between the bridge plate and lip moves them both
upwardly to a cocked position to which they are supported by the
toggle arm and lower link, which pivot into an over-center
position. Downward force exerted on the upper part of the bridge
plate causes a cam follower carried by the pivotal connection
between the toggle arm and lower link to engage a cam surface
mounted beneath the bridge plate. A coil spring mounted about the
lower pivotal point of the lower link exerts pressure against the
lower link, thereby counter-balancing the weight of the lip and
bridge plate during pivotal movement of the lower link in either
direction.
Inventors: |
Ellis; Lawrence D. (Monrovia,
CA), Evans; Robert E. (Pasadena, CA) |
Assignee: |
Ellis Industries, Inc. (South
El Monte, CA)
|
Family
ID: |
24310014 |
Appl.
No.: |
05/711,477 |
Filed: |
August 4, 1976 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
577754 |
May 15, 1975 |
3974537 |
|
|
|
Current U.S.
Class: |
14/71.3 |
Current CPC
Class: |
B65G
69/2841 (20130101); B65G 69/2894 (20130101) |
Current International
Class: |
B65G
69/28 (20060101); B65G 69/00 (20060101); B65G
011/00 () |
Field of
Search: |
;14/71.3,69.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Byers, Jr.; Nile C.
Attorney, Agent or Firm: Comstock; Robert C.
Parent Case Text
REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of our co-pending
application Ser. No. 577,754 filed May 15, 1975, now U.S. Pat. No.
3,974,537.
Claims
We claim:
1. A lip extender for use with a loading dock leveler of the type
having a vertically directed base plate, a bridge plate pivotally
connected to said base plate and a lip pivotally mounted along its
inner edge to the outer edge of the bridge plate, said lip extender
comprising a lower link pivotally connected at its lower end to
said base plate, a toggle arm pivotally connected at its upper end
beneath said lip, the opposite ends of said lower link and toggle
arm being constructed and arranged so that upon lifting of said
bridge plate, the pivotally connected ends of said lower link and
toggle arm move into an over-center locking engagement with each
other to hold said bridge plate and lip in an elevated position,
and a cam mounted beneath said bridge plate, said cam having a cam
surface, a cam follower carried by the pivotal connection between
said toggle arm and said lower link, and an elongated heavy duty
coil spring disposed adjacent to the lower end of said lower link,
one end of said coil spring bearing against said base plate and the
other end of said coil spring bearing against the lower end of said
lower link to counter-balance the weight of said bridge plate and
lip through said lower link and toggle arm.
2. The structure described in claim 1, said coil spring being
mounted directly adjacent to the pivotal connection between said
lower link and said base plate.
3. The structure described in claim 2, said coil spring being
mounted around an elongated cylindrical arbor, said arbor being
aligned with and disposed directly adjacent to the pivotal
connection between said lower link and said base plate.
4. The structure described in claim 3, said lip extender having a
pair of spaced side plates extending transversely to said base
plate, a shaft extending through said side plates, the lower end of
said lower link being pivotally mounted about said shaft, said
shaft extending through said arbor.
5. The structure described in claim 4, the end of said spring which
bears against said base plate extending into one end of a hollow
sleeve member, a bolt threaded through the opposite end of said
sleeve member, said bolt being adjustable to move the ehd of said
spring toward or away from said base plate to adjust the amount of
tension exerted by said coil spring against said lower link.
6. The structure described in claim 5, and resilient means urging
at least one of said lower link and toggle arm members into said
over-center relationship.
7. The structure described in claim 6, such resilient means urging
said cam follower into engagement with said cam surface.
8. The structure described in claim 1, the end of said spring which
bears against said base plate extending into one end of a hollow
sleeve member, a bolt threaded through the opposite end of said
sleeve member, said bolt being adjustable to move the end of said
spring toward or away from said base plate to adjust the amount of
tension exerted by said coil spring against said lower link.
9. The structure described in claim 1, said heavy duty coil spring
locking said bridge plate and lip in flat extended position to
prevent said bridge plate and lip from buckling out of extended
position.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for extending the lip of a
loading dock leveler for movement of the lip into the rear of a
truck disposed adjacent to the dock, and counter-balancing the
weight of the loading dock leveler for ease of operation.
2. Description of the Prior Art
Dock leverlers of the type now in use comprise a vertically
directed base plate which is permanently attached to the dock, a
bridge plate which is pivotally attached along one edge thereof to
the upper edge of the base plate, and a lip which is pivotally
attached to the opposite edge of the bridge plate.
At the present time, it is necessary for the operator to bend over
the edge of the dock, catch the bottom edge of the lip with a hook
or chain device and then lift the lip and swing it out into a
horizontal position. Since the operator is bending over the edge of
the dock, there is no firm support directly beneath him. The
operation requires a substantial amount of bending and twisting of
the back, frequently resulting in back injuries which are harmful
to the operator and costly to the employer.
There is no device in use at the present time which gives
substantial assistance in lifting the lip and/or in extending the
lip to its operating position.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a lip
extender and counter-balance mechanism for loading dock levelers
which eliminates the necessity for the operator to lift the lip
separately from the bridge plate lifting operation and which
thereafter automatically extends the lip into its operating
position without any lifting or bending action by the operator. In
addition, the mechanism applies a counter-balancing force to the
lip of the leveler which tends to lock the bridge plate and lip
into a flat position when extended, allowing the leveler to be
adjusted to provide lighter, easier operation than has ever before
been possible.
In essence, the invention contemplates a lip extending device which
automatically moves into operating position when the bridge plate
pintle pin is lifted. The device lifts the lip into an elevated
angular position with respect to the bridge plate and holds it
securely in such position. Downward force exerted upon the bridge
plate by the foot of the operator causes the lip to raise and
extend automatically into a horizontal position overlying the rear
edge of the truck simultaneously with movement of the bridge plate
into a horizontal position. When the leveler is horizontally
overlying the rear of the truck, the lip extender mechanism
automatically allows the leverler to drop onto the truck bed, while
locking the bridge plate and lip in a horizontal position to
prevent buckling and unwanted removal from the truck, which occurs
with present state of the art dock levelers.
With existing levelers, jostling of the bridge plate may result in
the spring causing the bridge plate to rise, carrying the lip along
with it. With the present invention, this cannot occur because the
spring exerts tension against the lip as well as the bridge
plate.
The present application relates to an improvement over our
co-pending application Ser. No. 577,754, now U.S. Pat. No.
3,974,537 in that it provides a coil spring which counter-balances
the weight of the lio and hinge plate during pivotal movement of
the lower link in either direction.
The device preferably includes a cam for automatically moving the
outer edge of the lip upwardly simultaneously with its outward
movement so as to clear the rear edge of the truck without any
lifting of the lip by the operator.
Another object is to provide a safer means of using the dock
leveler by having the operator place the leveler in use from a
position standing back on the dock instead of bending out over the
edge of the dock.
It is accordingly among the objects of the invention to provide a
lip extender for loading dock levelers having all of the advantages
and benefits of the invention set forth above and described in
further detail hereinafter in this specification.
Another object of the invention is to provide such a device which
is simple and economical in its construction and operation.
Still another object of the invention is to provide such a device
which can serve a secondary purpose of providing a block to prevent
rolling stock from accidentially falling off the edge of the
dock.
It is a further object of the invention to provide a device of the
type described which is adapted to be attached to and used with
substantially every edge-of-dock type dock leveler which is now in
use.
Another object of the invention is to provide a means for holding
the bridge plate and lip flat in order to prevent buckling and
unwanted accidental removal from the truck, which occurs with
present state of the art levelers.
The invention also comprises such other objects, advantages and
capabilities as will later more fully appear and which are
inherently possessed by the invention.
While there is shown in the accompanying drawings a preferred
embodiment of the invention, it should be understood that the same
is susceptible of modification and change without departing from
the spirit of the invention.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial transverse sectional view of the dock leveler
in normal out-of-use position;
FIG. 2 is a similar view showing the bridge plate and lip in
elevated or cocked position;
FIG. 3 is a sectional view taken on line 3--3 of FIG. 2;
FIG. 4 is a sectional view taken on line 4--4 of FIG. 3;
FIG. 5 is a sectional view taken on line 5--5 of FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment of the invention is adapted for use with
substantially any edge-of-dock type dock leveler now in use. For
purposes of illustration, one type of conventional dock leveler is
shown in the drawings, but the device is capable of being connected
to and functioning with substantially all other types of dock
levelers as well.
The conventional dock leveler structure includes a vertically
directed base plate 10, which is permanently fixed to the dock 11
and which extends downwardly from the upper edge of the dock 11. A
bridge plate 12, which normally extends horizontally outwardly from
the dock 11, is pivotally connected along one edge thereof to the
upper edge of the base plate 10 by a hinge 13.
The opposite edge of the bridge plate 12 is pivotally connected to
one edge of a lip 14, which normally hangs vertically downwardly
from the outer edge of the bridge plate 12. The pivot connection
between the bridge plate 12 and lip 14 comprises hinge means which
includes a pintle pin 15. The pintle pin 15 preferably extends
outwardly beyond one or both side edges of the bridge plate 12 and
lip 14 to provide a protuberance which can be caught by the end of
an elongated hook or chain device held by an operator for lifting
purposes.
The structure of the present invention comprises a square lower
plate 20 which is welded or otherwise secured to the base plate 10
of the dock leveler. A pair of spaced parallel side plates 21 are
welded or otherwise secured along one of their edges to the lower
plate 20. The lower plate 20 may be omitted and the side plates 21
welded directly to the base plate 10.
An upper plate assembly is welded or otherwise secured to the lower
side of the lip 14 directly above the pintle pin 15. The upper
plate assembly includes a pair of outwardly projecting side members
23, to each of which is welded an angle iron clip 24 which is
disposed at an angle with respect to the side member 23 to which it
is secured.
The clips 24 have threaded openings in the center of the portions
thereof which extend outwardly from the side members 23. A bolt 26
is threadedly mounted in each of the openings for adjustment
purposes. The ends of the bolts 26 are constructed and arranged to
engage the under side of the bridge plate 12 when the mechanism is
in cocked position. The bolts 26 are threadedly adjustable to
control their length and thereby control the angular projection of
the lip 14 as described herinafter.
Mounted on the under side of the bridge plate 12 adjacent to the
pintle pin 15 is a cam plate assembly which comprises a pair of
angle iron side plates 30 which are welded or otherwise connected
to the bridge plate 12 and to the opposite sides of a cam plate 31.
The cam plate 31 extends transversely with respect to the bridge
plate 12 and its outer edge comprises a curved cam surface 32
having at the lower end thereof an inwardly curved pocket or recess
33.
A lower link assembly comprises a lower link 34 having a pair of
sides 35 between which extend a pair of spaced angle iron
reinforcements 36. The lower end of the link 34 is pivotally
mounted on the shank of a bolt 37, which extends through one of the
side plates 21. The threaded inner end of the bolt 37 extends into
one end of an elongated arbor 80, which extends between the lower
link 34 and the other side plate 21. A second bolt 81 extends
through the other side plate 21 and has its inner end threaded into
the opposite end of the arbor 80.
An elongated heavy duty coil spring 82 is mounted concentrically
around the arbor 80, as shown in FIGS. 3-5 of the drawings. One end
83 of the spring 82 extends upwardly and bears against the
lowermost angle iron reinforcement 36 of the lower link 34. The
other end 84 of the spring 82 extends into the open end of a sleeve
member 85. Threadedly extending through the opposite end of the
sleeve member 85 is an adjusting bolt 86, the end of which bears
against the lower plate 20.
The bolt 86 may be rotated to move the lower end of the sleeve 85
toward or away from the lower plate 20 and thereby adjust the
amount of tension which is exerted by the opposite end 83 of the
coil spring 82 against the lower link 34.
Extending betwen the sides 35 at the upper end of the lower link 34
is a bolt 38. A cam follower 39 is rotatably mounted on the bolt
38. The cam follower 39 is adapted to engage and follow the cam
surface 32. Also rotatably mounted on the bolt 38 is a spherical
rod end 40, the rod portion 41 of which is threadedly connected to
the lower part of the toggle arm 42.
The upper end of the toggle arm 42 is rotatably journaled on a
shaft 43 which extends across the upper part of the upper plate
assembly, extending through the side members 23.
A torsion spring 45 concentrically surrounds an arbor sleeve 46
mounted on the shaft 43. One end of the spring 45 engages the
toggle arm 42 and the other end engages the under side of the lip
14.
When the dock leveler is aligned in its normal out of use position,
the bridge plate 12 extends horizontally and the lip 14 extends
downwardly in vertical position. Upon lifting movement exerted by
the operator on the end of the pintle pin 15 with a hook or the
like, the bridge plate 12 is pivoted upwardly on its hinge 13,
carrying the lip 14 along with it.
It should be noted that the heavy duty coil spring 82 exerts
pressure against the lower link 34 through engagement between the
end 83 of the spring 82 and the angle iron reinforcement 36 of the
lower link 34. The spring 82 thereby exerts pressure which assists
in lifting the weight of the bridge plate 12 and through the toggle
arm 42 also assists in lifting the weight of the lip 14. The lip 14
customarily weighs approximately 170 lbs. and the spring 82 helps
to reduce the amount of lifting effort which must be exerted by the
operator.
Upward movement of the lip 14 causes the lower link 34 to pivot
rearwardly toward the dock 11, pivoting on the pivot pin 37. At the
same time, the toggle arm 42 also pivots rearwardly toward the dock
11, pivoting on the shaft 43.
When the bridge plate 12 approaches a substantially vertical
position, lower link 34 and toggle arm 42 also reach substantially
vertical aligned positions. Further upward movement of the pintle
pin 15 causes the lower link 34 and toggle arm 42 to move to an
over-center position in which they are inclined slightly toward the
dock 11. The torsion spring 45 exerts pressure upon the toggle arm
42 to assure its movement into an over-center position.
The device is now in what may be termed a cocked position, as shown
in FIGS. 2 and 3 of the drawings. Movement beyond this position is
prevented by engagement between the ends of the bolts 26 and the
under side of the bridge plate 12 and by engagement between the cam
follower 39 and the cam surface 32. In this position, the cam
follower 39 is disposed within the recess 33 on the lower part of
the cam surface 32.
The dock leveler is now in position for movement of the lip 14 into
the rear of the truck. This is accomplished by exerting downward
and outward pressure on the upper portion of the bridge plate 12 in
the area adjacent to the pintle pin 15. This may conveniently be
done by the foot of the operator.
As pressure is exerted against the upper portion of the bridge
plate 12, the bridge plate 12 pivots forwardly, away from the dock
11. As the bridge plate 12 moves forwardly it causes the cam
surface 32 to move downwardly with respect to the cam follower 39.
As the cam follower 39 moves upwardly with respect to the cam
surface 32, it also moves outwardly due to the curvature of the cam
surface 32. Upward and outward movement of the cam follower 39 is
transmitted through the rod portion 41 to the shaft 43, causing
simultaneous upward and outward movement of the outer edge of the
lip 14.
This upward and outward movement of the outer edge of the lip 14
continues until the cam follower 39 approaches the upper end of the
cam surface 32, at which time the toggle arm 42 and lower link 34
are moved out of their over-center position. They accordingly no
longer support the bridge plate 12 and lip 14, which move to a
horizontal position. The coil spring 82 provides pressure which
resists but does not prevent the downward movement of the bridge
plate 12 and lip 14. The spring 82 accordingly provides a
counter-balancing effect during the downward movement.
In use, the truck which is disposed adjacent to the dock has a flat
horizontal cargo carrying bed which is on a level with or disposed
somewhat above or below the level of the dock. The rear of the
truck extends verticaly downwardly from a cargo carrying bed and is
disposed only a short distance outwardly from the edge of the dock.
The lip 14 is disposed vertically between the dock and the rear of
the truck.
In using the dock leveler, it is necessary first to move the lip
upwardly in such a manner that it will clear the rear of the truck.
The lip 14 must them be moved upwardly a sufficient distance to
clear the rear edge of the bed of the truck as the lip is moved
into it. The bed of the truck may be disposed above the level of
the dock or may have an elevated portion which is so disposed. The
device is preferably constructed and arranged so that the outer
edge of the lip is capable of clearing a truck disposed
approximately 6 inches above the level of the dock.
The device is provided with adjusting means for achieving the best
movement of the lip. The lip adjusting bolts 26 control the
distance between the outer edge of the lip 14 and the rear of the
truck when the leveler is being moved into its cocked position.
They may also be adjusted to provide maximum upward movement of the
lip for maximum clearance over the truck bed. The rod portion 41 is
adjustable with respect to the upper plate 17 to control the height
of the outer edge of the lip 14 when the toggle arm 42 and lower
link 34 move into and out of over-center position.
When the trust is loaded, it can be driven away from beneath the
lip 14, which will drop down into its vertical out of use position.
The lip 14 and bridge plate 12 may also be removed from the trust
by reverse movement of that described above.
Uppn such reverse movement, the coil spring 82 again acts to assist
in the lifting and reverse movement of the lip 14 and bridge plate
12 and counter-balances their weight during such movement.
When the device is in cocked position it can be left in such
elevated cocked position and used as a block to prevent the
accidental movement of rolling stock and /or personnel off the edge
of the dock.
While the term "lower link" has been used to designate the lower
link or toggle member and the term "toggle arm" has been used to
designate the upper link or toggle member, it should be understood
that such terms are not limiting and that any suitable pair of link
or toggle members may be used which accomplishes the results shown
and described.
* * * * *